The present invention provides a novel means for sensing the speed, direction and angular position of a vehicle steering shaft or column using a detachable or "clip-on" sensor mount containing multiple Hall-effect sensor elements.
Electronic control units (ECU) amass information from sensors and command the action of many vital functions in today's automobile. There are four major categories in which electronic controls have made substantial inroads: (1) engine, (2) transmission, (3) suspension, and (4) anti-lock braking/traction control. In all of these cases the signals of the rotational motion or position change of components are fed to the ECU, which compares them to a calculated or mapped value ideal for the operational conditions. The ECU then initiates changes in the controlled function in order to minimize deviation from ideal conditions. For this scheme to work effectively, high reliability, good resolution and economic sensor systems are required.
In order to sense motion/position in an automobile, there are four distinct systems that have evolved: (1) passive or variable reluctance sensors, (2) active sensors, such as Hall-effect sensors, (3) optical sensors, and (4) accelerometers. Variable reluctance sensors have been used predominantly in anti-lock braking systems (ABS) for wheel speed sensing and in automatic transmission output speed sensing. Hall-effect sensors have been used mostly in ignition systems, while optical sensors and accelerometers are used in suspension control systems.
Some of the major improvements in passenger comfort have been achieved as a result of improving the ride characteristics of automobiles. The improvements have been accomplished by, among other things, the introduction of active and semiactive suspension systems. Conventional systems sense lateral acceleration which is input into the ride control ECU. There are several ways of obtaining lateral acceleration. One popular way is to use steering column or shaft rotational position information (steering wheel angle) and the vehicle speed for calculating the resulting acceleration.
The need for sensing the position of automobile steering columns or shafts has developed because of active suspension systems, electronic power steering assistance, safe driver warning systems, and four wheel steering. As such, various sensors have been created to detect speed, direction and a reference pulse (i.e., true position). The conventional means for obtaining steering wheel angle information is an optical sensor system or an accelerometer.
The present invention relates primarily to the use of Hall-effect sensors to detect the speed, direction and position of an automobile steering column or shaft. The sensor bearing according to the present invention utilizes the precision of existing steering shaft support bearings. Other advantages involve weight and cost savings, insensitivity to dirt or foreign matter, simple mounting, high resolution, and an easy way to achieve a true reference position.
Moreover, the present invention provides a much more simplified design verses conventional optical sensors with the added benefits of "clip-on" sensor mounting, directional sensing and reference pulse recognition.
Additional advantages of the present invention shall become apparent as described below.